Reviving An 8-Inch Hard Drive From The 1980s

August 8, 2023 by Maya Posch 17 Comments

As part of the eternal quest within the realm of retrocomputing, storage devices can be one of the most challenging, especially when it comes to firmly obsolete hard drives, such as the CDC Finch drive. This compact 8″ HDD replaced the previous 14″ models with a form factor that was decidedly more portable. These Finch drives being 1980s technology that got run pretty hard before their retirement, it’s little wonder that they’d end up on the repair bench over at [Usagi Electric]

A CDC Finch hard disk drive, available in 8 to 32 MB for all your data storage needs. (Credit: Usage Electric)

Introduced in the early 1980s, the CDC Model 9410 Finch drive was unlike its 14″ predecessors in that it is a sealed unit, with maintenance-free air filtration. With the 14″ models you’d have both fixed and swappable platters, with far less consideration for dust exposure. This makes these Finch drives more touchy to work on, not unlike HDDs today, and adds to the excitement when repairing one of these old drives.

In this video, two differently broken Finch drives are discussed. Both appear to have an issue on the controller board, with one not responding to communications on the interface, while the other featuring a dead short on the interface pins. The first drive was brought back to life by replacing a dead SN75110 line driver IC, as well as a dead 7818 voltage regulator that was only outputting a sad 0.3 V.

Unfortunately, after half an hour of uptime and in the process of dumping data the drive errored out with a Not Ready, indicating that there are further issues on the controller board to fix. The good news here is that the platters appear to be pretty robust, but the controller boards on these old drives tend to develop issues over the years, something which will be further explored in upcoming videos.

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Enhance Your Enclosures With A Shadow Line

August 7, 2023 by Donald Papp 15 Comments

Some design techniques and concepts from the injection molding world apply very nicely to 3D printing, despite them being fundamentally different processes. [Teaching Tech] demonstrates designing shadow lines into 3D printed parts whose surfaces are intended to mate up to one another.

This is a feature mainly seen in enclosures, and you’ve definitely seen it in all kinds of off-the-shelf products. Essentially, one half of the part has a slight “underbite” of a rim, and the other half has a slight “overbite”, with a bit of a standoff between the two. When placed together, the combination helps parts self-locate to one another, as well as providing a consistent appearance around the mating surfaces.

Why is this necessary? When a plastic part is made — such as an enclosure in two halves — the resulting surfaces are never truly flat. Without post-processing, the two not-quite-flat surfaces result in an inconsistent line with a varying gap between them.

By designing in a shadow line, the two parts will not only self-locate to each other for assembly, but will appear as a much more consistent fit. There will be a clear line between the two parts, but no actual visible gaps between them. Watch the whole thing explained in the video, embedded below.

This isn’t the only time design techniques from the world of injection molding have migrated to 3D printing. Crush ribs have been adapted to the world of 3D printed parts and are a tried-and-true solution to the problem of reliably obtaining a tight fit between plastic parts and hardware inserts.

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Linux Containers The Hard Way

August 7, 2023 by Al Williams 10 Comments

If you want to make containers under Linux, plenty of high-level options exist. [Lucavallin] wanted to learn more about how containers really work, so he decided to tackle the problem using the low-level kernel functions, and he shared the code with us on GitHub.

Containers are more isolated than processes but not quite full virtual machines. While a virtual machine creates a fake computer, a container is more like a fake operating system. Applications can run with their own idea of libraries, devices, and other resources, but it doesn’t try to abstract the underlying hardware.

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When The Sojourner Mars Rover Nearly Ran LISP

August 7, 2023 by Maya Posch 11 Comments

During the late 1980s NASA’s Jet Propulsion Laboratory (JPL) was busy developing the first ever wheeled robot that would roam the surface of Mars. Due to the long round-trip times of any signals between Mars and Earth, development of the firmware that would control the rover was a major point, with the two teams occupied with the task each picking different levels of autonomy for the rover. In a retrospective, [Ron Garrett] who worked at JPL on the ‘more autonomy’ team describes his recollections.

Whereas [Ron]’s team focused on creating a rover that could be provided with high-level instructions which the sophisticated LISP-based firmware would use as guidelines to navigate and operate by, the other team pursued a more limited autonomy approach whereby a human driver would use explicitly plan out the route which the rover would follow before awaiting new instructions.

Perhaps unsurprisingly, the system requirements for running LISP and the additional uncertainties and complexities with the autonomous approach, as well as testing and validating the firmware, resulted in the Sojourner Mars rover featuring the latter approach, with straightforward C-based firmware. Most of Sojourner’s autonomy was limited to a home return function if communication with the lander was lost, which limited both its range and operations during its 85-day extended mission.

As [Ron] covers with examples from later missions, one advantage of LISP is that it allows you to send instructions which can be interpreted (e.g. to debug the system) without having to program in such functionality explicitly. With later Mars rover missions much more of this autonomy that [Ron]’s team pioneered was implemented, although C remained the language of choice for these later rovers.

Heading image: Ron Garrett standing in front of the Robbie prototype. Rocky III can be see in the lower left, and above him are Rajiv Desai and Robert Ivlev, two other members of the team. (Credit: Ron Garret)

The Egyptian Coin Box ‘Trick’

August 7, 2023 by Dave Rowntree 9 Comments

[James Stanley] likes to spend time making puzzles and gadgets for escape rooms, and decided for a change to try their hand at a bit of magic. The idea was to construct a ‘magic box’, in which a coin can be placed in one of a number of slots, and then be able to remotely be able to determine the slot by means unseen. Obviously, this is an electronics hack, with a neat package of sensor and radio comms hidden inside a stack of CNC-milled wood. Coin locations are transmitted via Bluetooth to a Bangle.js smartwatch, which vibrates according to the slot occupied, allowing [James] to predict where the coin was placed. Continue reading “The Egyptian Coin Box ‘Trick’” →

Showing pulse oximeter and color sensor combining to measure oxygen in blood and skin tone

Perfecting The Pulse Oximeter

August 7, 2023 by Orlando Hoilett 28 Comments

We’re always looking for interesting biohacks here on Hackaday, and this new research article describing a calibrated pulse oximeter for different skin tones really caught our attention.

Pulse oximeters are handy little instruments that measure your blood oxygen saturation using photoplethysmography (PPG) and are a topic we’re no strangers to here at Hackaday. Given PPG is an optical technique, it stands to reason that its accuracy could be significantly affected by skin tone and that has been a major topic of discussion recently in the medical field. Given the noted issues with pulse oximeter accuracy, these researchers endeavored to create a better pulse oximeter by quantifying skin pigmentation and using that data to offset errors in the pulse oximeter measurements. A slick idea, but we think their results leave a lot to be desired.

Their idea sounds pretty straightforward enough. They created their own hardware to measure blood oxygen saturation, a smartwatch that includes red and infrared (IR) light-emitting diodes (LED) to illuminate the tissue just below the surface of the skin, and a photosensor for measuring the amount of light that reflects off the skin. But in addition to the standard pulse oximeter hardware, they also include a TCS34725 color sensor to quantify the user’s skin tone.

So what’s the issue? Well, the researchers mentioned calibrating their color sensor to a standard commercially-available dermatology instrument just to make sure their skin pigmentation values match a gold standard, but we can’t find that data, making it a bit hard to evaluate how accurate their color sensor actually is. That’s pretty crucial to their entire premise. And ultimately, their corrected blood oxygen values don’t really seem terribly promising either. For one individual, they reduced their error from 5.44% to 0.82% which seems great! But for another user, their error actually increases from 0.99% to 6.41%. Not so great. Is the problem in their color sensor calibration? Could be.

We know from personal experience that pulse oximeters are hard, so we applaud their efforts in tackling a major problem. Maybe the Hackaday community could help them out?

All About USB-C: Example Circuits

August 7, 2023 by Arya Voronova 8 Comments

In the six months that have passed after the last USB-C article has been released, I have thought up a bunch of ways that these articles could have been improved. It’s, of course, normal to have such a feeling — expected, even. I now believe that there’s a few gaps that I could bridge. For instance, I have not provided enough example circuits, and sometimes one schematic can convey things better than a thousand words.

Let’s fix that! I’ll give you schematics for the kinds of USB-C devices you’re actually likely to want to build. I’ll also share a bunch of IC part numbers in this article, but I don’t have an exhaustive collection, of course – if you find more cool ICs that work for USB-C purposes and aren’t mentioned here, please do let us all know in the comments!

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